"Use your Einstein formula!" he screeched. "How far? I'll tell you. _One
second!_" He grinned triumphantly. "That's how possible it is to travel
into the future. And as for the past--in the first place, you'd have to
exceed light-speed, which immediately entails the use of more than an
infinite number of horsepowers. We'll assume that the great engineer
Dixon Wells solves that little problem too, even though the energy
out-put of the whole universe is not an infinite number of horsepowers.
Then he applies this more than infinite power to travel at two hundred
and four thousand miles per second for _ten_ seconds. He has then
penetrated the past. How far?"
Again I hesitated.
"I'll tell you. _One second!_" He glared at me. "Now all you have to do
is to design such a machine, and then van Manderpootz will admit the
possibility of traveling into the future--for a limited number of
seconds. As for the past, I have just explained that all the energy in
the universe is insufficient for that."
"But," I stammered, "you just said that you--"
"I did _not_ say anything about traveling into either future or past,
which I have just demonstrated to you to be impossible--a practical
impossibility in the one case and an absolute one in the other."
"Then how _do_ you travel in time?"
"Not even van Manderpootz can perform the impossible," said the
professor, now faintly jovial. He tapped a thick pad of typewriter paper
on the table beside him. "See, Dick, this is the world, the universe."
He swept a finger down it. "It is long in time, and"--sweeping his hand
across it--"it is broad in space, but"--now jabbing his finger against
its center--"it is very thin in the fourth dimension. Van Manderpootz
takes always the shortest, the most logical course. I do not travel
along time, into past or future. No. Me, I travel across time,
sideways!"